Use fcntl.h for dev_t & mode_t

Should fix:

In file included from /usr/include/bits/statx.h:31,
                 from /usr/include/sys/stat.h:446,
                 from include/files.h:3,
                 from include/shm.h:6,
                 from syscalls/x86/modify_ldt.c:12:
/usr/include/linux/stat.h:57:2: error: unknown type name ‘__s64’
  __s64 tv_sec;
  ^~~~~
/usr/include/linux/stat.h:58:2: error: unknown type name ‘__u32’
  __u32 tv_nsec;
  ^~~~~
/usr/include/linux/stat.h:59:2: error: unknown type name ‘__s32’
  __s32 __reserved;
  ^~~~~
/usr/include/linux/stat.h:101:2: error: unknown type name ‘__u32’
  __u32 stx_mask; /* What results were written [uncond] */

include/files.h

@@ -1,6 +1,6 @@
 #pragma once
 
-#include <sys/stat.h>
+#include <fcntl.h>
 #include "fd.h"
 
 unsigned long get_o_flags(void);